Maize (Zea mays L.), an important source of calories and nutrients in sub-Saharan Africa, is threatened by northern corn leaf blight (NCLB) caused by Exserohilum turcicum. This study examined combining ability and heterotic patterns of early-maturing maize inbreds, gene action conditioning NCLB resistance, and performance of derived hybrids across environments and identified testers. Fifteen each of white and yellow inbreds were intercrossed using North Carolina Design II to obtain 75 hybrids per endosperm color. Hybrids plus six checks were inoculated with a virulent isolate of E. turcicum 4 wk after planting in six inoculated and three non-inoculated environments in Nigeria in 2018 and 2019. Inbreds were assigned to heterotic groups using general combining ability (GCA) of multiple traits method. Specific combining ability (SCA), GCA, and genotype × environment (G × E) interactions were significant for grain yield (GYLD), disease severity, and other traits. Northern corn leaf blight caused 46% GYLD reduction. The effects of GCA were preponderant over SCA for GYLD and NCLB severity across environments, indicating that hybridization and recurrent selection would enhance genetic gains and hybrid performance. White and yellow inbreds were placed in two and three heterotic groups, respectively. High-yielding NCLB-resistant testers identified could be used to classify other inbreds yet to be field-tested into heterotic groups. Genotypes TZEI 32 × TZEI 5 and TZEI 124 × TZEI 134 were identified as single-cross testers. Genotypes TZEI 32 × TZEI 5 and TZEI 5 × TZEI 75 (white) and TZEI 124 × TZEI 134 and TZEI 124 × TZEI 11 (yellow) were identified for on-farm testing and possible commercialization.

中文翻译：

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抗柑橘早熟玉米自交系的配合力及杂种优势分组

玉米 ( Zea mays L.) 是撒哈拉以南非洲重要的热量和营养来源，受到Exserohilum turcicum引起的北方玉米叶枯病 (NCLB) 的威胁。该研究检查了早熟玉米自交系的结合能力和杂种优势模式、调节 NCLB 抗性的基因作用，以及衍生杂交种跨环境和鉴定测试者的表现。使用 North Carolina Design II 将 15 个白色和黄色近交系杂交，以获得每种胚乳颜色的 75 个杂种。杂种加上六个检查接种了E. turcicum的毒力分离株2018 年和 2019 年在尼日利亚 6 个接种环境和 3 个非接种环境中种植后 4 周。使用多性状方法的一般配合力（GCA）将近交种分配到杂种优势组。特定配合力 (SCA)、GCA 和基因型 × 环境 (G × E) 相互作用对谷物产量 (GYLD)、疾病严重程度和其他性状具有显着意义。北方玉米叶枯病导致 GYLD 减少 46%。对于跨环境的 GYLD 和 NCLB 严重程度，GCA 的影响优于 SCA，表明杂交和循环选择将提高遗传增益和杂交性能。白色和黄色自交系分别被置于两个和三个杂种优势组中。鉴定出的高产 NCLB 抗性测试者可用于将其他尚未进行田间试验的近交系分类为杂种优势群体。基因型 TZEI 32 × TZEI 5 和 TZEI 124 × TZEI 134 被鉴定为单交叉测试者。基因型 TZEI 32 × TZEI 5 和 TZEI 5 × TZEI 75（白色）和 TZEI 124 × TZEI 134 和 TZEI 124 × TZEI 11（黄色）被确定用于农场测试和可能的商业化。